Numerical simulation study on the mechanical properties of rectangular pipe jacking tunnel joints with longitudinal connectors

• Comprehensive study on rectangular pipe jacking tunnel joints. • Advanced 3D finite element modeling. • Validation with experimental data. • Findings on joint damage and stress concentration. • Multi-section model for realistic conditions. The joint of rectangular pipe jacking tunnel is critical component that ensures the structural integrity under applied loads. As the weakest part of the tunnel structure, the mechanical behavior of the joint plays a decisive role in the overall mechanical performance. To investigate this, a three-dimensional refined finite element model was developed to analyze the mechanical performance and deformation behavior of rectangular pipe jacking tunnel with F-type socket joint equipped with longitudinal connectors under shear and bending loads. Additionally, a five-section model was constructed to simulate deformation and failure characteristics under more realistic conditions. The research results indicate that the joint exhibits significant contact nonlinearity, with deformation characterized by pronounced discontinuities. Under shear loading, damage is primarily concentrated around the bolt holes, chamfered areas, and the top and bottom plates. Stress concentration is particularly evident at the chamfer of the steel ring, with the straight bolt connection showing a higher degree of stress concentration in the steel ring compared to the bent bolt connection. Under bending loads, severe concrete damage is observed at the top plate of the joint, with a wider distribution of damage in the bent bolt connection. The straight bolt connection performs better in enhancing joint integrity and resisting deformation than the bent bolt connection. Increasing the diameter of the longitudinal connector has a limited effect on reducing joint deformation, whereas reducing the clearance between the bolt hole and the connector can significantly enhance the joint’s initial resistance to deformation. The expected conclusion is intended to provide a theoretical basis for the optimized design and engineering application of rectangular pipe jacking tunnel joints.